Introduction into Batteries and Charging Systems

[Deezelweazel]

7. Fuses and Connectors:

Warning:
The most overlooked items in vehicle wiring are fuses and connectors.
Most of the time the source for problems is located here.
In our application a cheap ass wiring is simply expressed dangerous.
We are dealing with currents high enough to weld or to set our Jeep onto a nice campsite fire.

- Fuses
Even if the purpose of a fuse is always the same, there are differences out there:

Don't get fooled by shiny fuse holders using gold plated connectors. If you want to spend the money. Ok, just go ahead.
It is not necessary.
Gold is used in applications where contact resistance is important. In a 12 V system resistance is an issue.

I'm not saying gold plated fuses are bad- you just have to look at the type.
There are a couple of different fuse systems out there:

- Automatic fuses
automatic fuse resistance: fluctuating up to 200milliΏ
Lets start with automatic fuses.
They have the advantage that you can open the circuit with a flick of a switch when necessary.
Sadly the contact resistance of these devices is very high. This causes a voltage drop and we have to fight for every tenth of a Volt!
Automatic fuses are a NONO for our application!

The worst fuse of all- convenient, but not for our application:




- glass type fuses
As the name says glass type fuses use a fuse that is covered in a tube of glass. Usually this tube is held by springs bent around the tube. Contact depends on the pressure of the springs. Resistance therfor depends also on the springs.
Touching the contact area with bare fingers also adds grease onto the contacts.
Spring pressure decreases over time. Contact resistance is to high. Avoid glass type fuses. I know the car hifi guys go: "yaddayadda not true..."
It is true - simply do the measurement with a DMM in your complete application and you will see.
glas type fuse resistance: 2.4 milliΏ

A typical glass tube fuse:






- ANL fuses and Mini ANL fuses.

Now we are coming to the real stuff.
Both, ANL and mini ANL fuses use real bolts and nuts to tighten the fuse blade in place.
Contact resistance is the lessest of all available fuse types so this is the way to go.
Just make sure to have a couple of spare fuses at hand since they are not available on the road.

ANL fuses are available in gold plated or tin plated. It depends on your wallet what you want to spend.
ANL-fuse resistance: 0.16 milliΏ

This is what an ANL fuse+ fuse mount looks like:
As you can see the center block is made out of concrete or ceramic- avoid the resin or plastic made ones.



Hint:
Good fuses do have a small window inside the fuse element. This prevents sparks or glowing pieces of metal to fall out in the event of failure. This is a quality indicator!

The proper way to hold a fuse- avoid touching the contact area with the fingers- to much grease!:




Do not think:
" Ha, I'm gonna save on resistance and I will not use any fuse"
Believe me it is no fun to try to rip out or to extinguish a glowing 35mm² cable.- You won't make it!

There is a reason for all these fuse thoughts:
You have a battery in the back of your car which is a high potential source of power and you have a source of power- the alternator.
A conductor coming into contact with the grounded frame produces a nice firework of sparks.
You need to fuse the wiring from the alternator and the battery itself. therfor the need of two fuses when using an aux battery.
The first must be placed directly behind the isolator.
The other must be placed in front of the battery.

It can't be overstressed. Do not skip on two fuses!
It must be mentioned here:
After inserting the two ANL fuses in line the supply battery voltage at the battery itself dropped by 0.1V. It is not much, but even the lowest drop is measureable!
It still has no effect on the battery charge. I just want to mention it.


- Connectors
Soldering or crimping? Maybe both?
Modern applications scream for crimping!

Why?
Easy to explain: Crimping is prefered (also called cold welding); Contact resistance is lowest and contact corrosion is avoided.
In a soldering connection the lead adds resistance and the connection is getting hard. That means the possibility of a fracture at the connection due to vibration is very high.
secondly the flux being used to get rid of corrosion during soldering is aggressive. You can't get rid of it. After a while the flux attacks the wiring and the connector. Corrosions sets in. And with Corrosion resistance does come- we don't want that!

Spend the money and get your connectors crimped. Do not think of buying a crimping tool. In this diameter being used professional crimping pliers are expensive.

Stay away from positap's, T-taps, 3M taps, T-locks or any name they might have and do look like this:
They offer quick connections- with aprice a couple of weeks or months and they start to get loose, or to rust. Enjoy the fun to seek for the cause.
Do yourself a favor- just stay away from them.






- Resistance

While at it we need to talk about restistance:
Copper is the most favoured material in automotive applications.
Since everybody tries to sell cheap stuff watch out for cable marked with CCA.
This is no copper cable - it is:
Copper Cladded Aluminum- it is aluminum with a surface treating of copper. You won't recognize the difference.
BUt- it has 30% more electrical resistivity than copper. So be alerted when you found some super cheap cable.

Tip:
Go into a welding supply shop. You can get your OFC (Oxygen Free Copper) cable for a fraction of the price than in a camper or boat supply shop.

How to calculate resistance of a cable:

We need a formula for this:

R is the electrical resistance of a uniform specimen of the material (measured in ohms, Ω)

l is the length of the piece of material (measured in metres, m)

A is the cross-sectional area of the specimen (measured in square mm²).

As you can see the thicker the diameter of the cable, the shorter the cable, the better the material of the cable the less loss we have.

Depending on the application minimum cable diameter is given to achieve a low loss.

There are two categories:

- Sensitive equipment demanding for a voltage drop less than 0.3V

- Standard equipment demanding for a voltage drop less than 1.0V

To charge a battery we must keep the voltage drop as low as possible.

The higher the flowing current the higher the loss.

The following chart gives you a comparision between materials. That P (roh) is the electrical resistivity - the less the number the better (lesser) the electrical resistivity :

Silver p = 0,015

Copper p= 0.01786

Aluminum p= 0.0278


Connectors can be had in all sizes and shapes. Gold plated or simply tinned.
It depends on your choice what to spend.
Just make sure the base material is copper or brass.
During my beginning I loved the gold plated style. After a couple of years I found out it only helps the dealer to justify the high price tag...

Hints:
Make sure you use ring eyelets- don't use open spades.
A loose connection will stay in place with a ring eyelet. An open spade will slip out of the stud and can cause serious damage.
Use the correct size of eyelets. A 10mm eyelet is not made for an 8mm stud.

Use heat shrinking tubes to isolate the eyelet.
It does look professional and gives you additional safety against unwanted shorts.
Always have in mind Murphy and his law is always there.

Choosing the proper cable diameter for your application:

Depending on your application you need to invest some thoughts about cable diameter.
In a dual battery setup the maximum current is the current delivered from the alternator.
But this is only true if you use a real diode isolator!

With a relay the batteries can always draw a significant higher current draw from the other battery!

The cables should be appropriate to the alternator and the length of the connection.
You find the correct diameter according to the length down in chapter 11 in the Comparison charts.

[Deezelweazel]

8. Battery watch relays

-What is is it?
Depending on the application undervoltage protection for your battery is necessary to prevent deep discharge.
Undervoltage protection, not to be confused with a battery monitor, triggers an alarm when the voltage drops below a certain level (e.g. by sounding a buzzer).

-How do they work?
When the voltage level falls below the second voltage threshold, connected loads are switched off. This guarantees battery start-up and prevents deep discharge, as well as increasing the batteries' service life.
disadvantage is that these devices consume also a bit of current. Even when the own current consumption is very little (usually around 20mA) This sums up to an remarkable amount of 14.4 Ah within a month. If you use your aux battery just occassionally without recharging you might start into your vaccation with a complete depleted battery.
Keep an eye on this devices...

I was thinking about these devices, but came to the conclusion that in my application the disadvantage is no relation with the effect.
I do list them here because I know if using a fridge a device like the Battery watch relay might come very handy.
A good device to protect the expensive battery.

[Deezelweazel]

9. The setup in a XJ with real life measurements:



- Setup in a XJ
So finally we found out we need a second battery in our Jeep or trailer.

In my case I wanted to supply an coolant engine heater to warm up the engine to operational temperatures before leaving to work.
Battery space in a XJ Diesel is limited. The biggest battery I could fit would be a 72Ah battery.
This really does not impress me!

- Calculations

Before we can start we need to know what we want to supply, the current consumption and the duration it has to be powered..

In my case the coolant engine heater has a power consumption of 45W per hour. If I want to use the interior heater fan I have to add additional 150W per hour.

The coolant heater needs a cycle of half an hour for a single operation.
This is necessary twice a day. travelling to work and back home.
During the summer months I don't need the interior fan.

Adding up I have a wattage of 200W in one hour.
Dividing it by 12V I get a current consumption of 16.6A.
Because this current is drained from the battery it is a discharge of 16.6Ah.

If I would try to do this with a single starter battery the battery would be damaged pretty soon. It is just intended to start the car.
Having in mind that a common starter battery is just charged with 2/3 of its capacity. This would give me a real life capacity of about 50Ah using a 72Ah battery.

What have I done?
I went with batteries for their special purpose.

Even knowing the Optima batteries having a bad reputation latelyI went with them.
(The first Optima I bought in 2000 is still used in the car of my son.)
The starter battery is an Optima Red top, a starter only battery being able to deliver the high currents for starting a diesel.

The supply battery was a Lifeline 105Ah AGM battery. Due to the unnecessary size and weight I traded with a friend for a brand new Optima Yellow Top.
Both batteries, the red top and the yellow top, have a capacity of 50Ah. adding up to 100Ah together.

The capacity of the Optima is only the half compared with the Lifeline. but according to the need more is simply not necessary. I don't want to carry more weight than necessary.
With the use of the Optima I discharge the supply battery down to 80% of the capacity. The battery is recharged, of course, while driving.
I plan to add an audio amplifier to the supply battery in the future, if I can find a place to mount the amplifier invisible.


Earlier we had a look onto the alternator- my alternator is a 117A model.
Having no fuel pump or injection system the full output can be instantly used to recharge the batteries.
Due to the high output I can recharge both batteries simultaneous.
Absolutely no need for priority charging.

- Execution
After knowing the current demand, the needed battery size to achieve extend charge cycles and therefor a long lifetime of the battery we can start to build our system.

After doing my research as seen above I had to come to a conclusion which battery isolator to use.
Having a military background the decision was relatively easy. Most relays being used in the military have been costly exchanged with diodes.
Listening to my mudding friends and complaining about the used relays my decision was made really quick.
Having a Jeep with an external regulator supported this idea.

The external regulator compensates the voltage drop for free!
I also loved the idea of having no internal moving parts.
I went with a diode isolator since the price offered to me with military discount was the same as an inferior relay.

A lot of mis-information about diode isolators is floating around the internet.
Mostly spread from people not knowing how to work with them.

The true statement that diodes have a voltage drop is only the half truth.
The other truth is how it is compensated, and that is what most people do not understand.


The basic set-up is clear:

A dual battery set-up consisting of a starter AGM battery and a supply AGM battery:
- Optima Red Top 50Ah
- Optima Yellow Top 55Ah

A diode isolator:
- Sure Power SP1302 with dual outputs and a maximum current of 130A

Fuses:
- ANL fuse holder made by Blue Sea using stainless steel studs.
- 100A ANL fuses

Cable:
- 10m of OFC 35mm² highly flexible copper cable bought from a local welding shop
(the length I bought was way to much, but I hate to run twice.)

The diameter of 35mm² was choosen acording to the maximum alternator output of 117A. Since I'm running a diode isolator I don't have to worry about current robberies from the other battery.
That also explains that current draws can never exceed the maximum alternator current.
This makes the wiring very safe.

Connectors:
- 8mm copper ring eyelets tin plated, to be crimped

Additional stuff:
- heat shrinking tube
- rubber caps to isolate studs (VTE)
- automotive protection tubes to cover the cable
- a piece of rubber used to isolate metal surfaces
- some tie-raps to lock cable in place
- Battery monitor BM 1 Nasa instruments, to control charge and discharge currents
- quick battery disconnect for the supply battery.

How does it look like?

This is the battery box.
Instead of a plastic box like Go-Jeep has used in his application I use an insulated Range bag from 5.11 Tactical.
The Optima fits perfectly into it.

It offers thermal insulation which keeps temperature differences in the winter at bay. the next advantage is the ziplock and the velcro closing.
An additional bonus is the supplied carrying strap.- Just put the strap on the bag and carry it around the neck to the place where you need the battery.
Cable entry is very easy to do.

The stealth effect. It looks like a boring tool box. An Optima yellow top in the back wouldn't sit there a long time- befor it would disappear...
Now it looks like a boring Optima in a boring bag...

The floor is fabricated from a 10mm thick rubber mat. It helps a lot, if you have a dog, that loves to play in the mud. And I know- ours does!





I opened the battery bag, so you can have a peep inside. The battery bag is tied down with two straps to the frame.There is no up and down or for/backward motion.

On the upper left you see the second Blue Sea fuse box. I do carry two 100A spare fuses.
On the lower right you see the measuring shunt- I still have to find an insulating box for that.
I'm not too happy with that arrangement.
Still looking for a complete insulated housing. I don't like to have any wires loose in a bag.
I also have to replace that groundstrap from the shunt to the negative battery pole. It was delivered with the battery monitor and is made too cheap. No insulation, cheap a$$, stiff and thin cable.

Those quick battery disconnects are very nice to work with.
They are made in Sweden and do lock the batterypoles very tight:





A couple of measurements can be seen in the following pictures:

This is the voltage measured right behind the alternator, before the diode isolator:

15.26 V





This is the voltage been measured behind the diode isolator:

14.55V



As you can see, there is no voltage drop, when done correctly.
The internal voltage drop being compensated is:
15.26V - 14.55V = 0.71V
Which indicates the use of a Schottky diode.



as you can see, voltage depends on charge state, length of the wirng, diameter and battery itself.
But:
There is simply no over- or undercharging of your expensive batteries.
Sorry for the small picture- I compressed it to much:

This is the voltage at the supply battery and the momentary current charge at 80%:
14.2V







Power loss in the Diode isolator

The diode isolator has some heat sink fins. They are needed for a purpose.
Here is the reason:
Diode isolator dropping voltage across input and output of the isolator is 0.71V. Now lets assume a charge current of both batteries, starter and supply, of 10 A each.

P= Ux I
P= 0.71 x (10A starter + 10A supply)
P= 14.2W
Heat loss in the isolator is 14.2 W. Thats not a lot of heat- in fact we will not even recognize it.

Heat loss at 100A will be 71W at the diode. That's a lot!
Diodes aren't allowed to reach a interior core temperature higher than 76°, otherwise they will reach their so called "second breakdown limit" and when reaching that they will burn up.
The reason for having that huge heat dissipating fins is to ensure safe operating temperatures.
This also explains the demand to mount the isolator to a solid metal surface.

[Deezelweazel]

10. Battery Monitor or Battery Management Systems

Battery monitors are simply expressed microprocessor-controlled measurement and monitoring system for your batteries. Most of the systems being sold use the so called Peukert equitation of measure charge and discharge of a battery.

These monitors records charging and discharging currents, including intermediate charges, and permanently calculates the current battery charge state taking a correction factor into account.
The charge state can be shown either in amp-hours (Ah) or as a percentage. Charging and discharging currents as well as battery voltage can also be read off on the display.

This gives us an permanent overview of the performance of chargers, current generators such as solar and wind generators and their electronic control units.

The high degree of precision also allows us to record the smallest discharge currents which, over a longer period, have a significant affect on the capacity available.
All of the information can be read on a display with an illuminated background. The measurements can be stored and saved even if the power supply is switche off.

A relay output is usually offered as an option:
if capacity or voltage values are exceeded or undershot it can, for example, trigger a buzzer to indicate an insufficient charge state.
Mostly these switching points can be freely programmed by the user.

Why is a battery monitor important to us?:
The battery monitor gives you a real time indication of the aux battery charge.
As we have learned above the lower the discharge the more life cycles you get. the battery monitor is way more precise than a voltmeter.
It tells you exactly how much charge is left and when to switch off the conneted devices.

Ok, the battery monitor also has its own current consumption. The current is around 1.5mA- no typo here: 0.0015A! Thats about
1Ah per month. This is less than the battery discharge itself! I think this is acceptable.

The battery monitor tells us excatly how much charge is left in the battery at the moment. Would you go without a fuel level gauge? The battery monitor is the same for the battery. Just telling you in real time how much "playtime" is left in the battery.

To give an example how the monitor can look like:
In this picture you can see a bunch of information given by the monitor:



Battery voltage is 12.3V with a discharge current of 11.6A. Battery still has 80% of it's capacity left.

Here you can see the difference between a voltmeter and a monitor.
The monitor knows how much capacity is left:
- by calculating with the known capacity of the battery
- by the discharge current
- time
- voltage
- and temperature

A voltmeter leaves you with guessing:
- because as we know 12.3 Volt is about 50% of charge (according to the comparison chart above).
Have also in mind that a battery voltage has to be read after sitting about 24 hours with no connection before measuring battery voltage.

Battery monitors are connected in line with the battery- usually a shunt is used right before the negative battery pole.
All currents and voltages going in and out are measured via this shunt.

[Deezelweazel]

11. Charts:
The following chart is taken from a specialized german car audio site, called auto- hifi
I do not own any rights on that drawaing.
It is is used for the ease of reading the correct cable diameters at certain lengths with the applied load:

Legend:
upper line: total wattage measured in watt
left side: length of the wiring
bottom line: fuse necessary to protect the circuit
numbers in the field: square diameter in mm²


How to use this chart:
Lets say you have a supply battery with a current draw of 50A max and 5 meters of cable distance:
Step 1:
calculating the wattage

50 A x 12 V= 600W
Looking into the chart you can see that 600 W is at the end of 25mm² and at the beginning of the 35mm² chart.
For safety purposes you choose the bigger cable diameter!
The proper fuse to choose is between 75A and 100A.
If you choose the smaller value the fuse might trip.
So choosing 100A is ok for the cable diameter delevering us a low resistance and a safe connection of fuses.
Remember! You need to use two fuses!
The mounting location of the fuses shouldn't be further than 30cm or 1 foot away from the power source.




Interesting fact is that two times 20mm² makes up for 70mm², this is caused due to the fact that audio applications do not have a permanent load. For continious load you must use the same diameter : 2 x 35mm²= 70mm²!
Have in mind, that two strands are ways easier to mount than one single cable.


How to convert AWG to mm²:

American Wire Gauge (AWG)	Diameter (inches)	Diameter (mm)	Cross Sectional Area (mm2)
0000	0.46	11.68	107.16
000	0.4096	10.40	84.97
00	0.3648	9.27	67.40
0	0.3249	8.25	53.46
1	0.2893	7.35	42.39
2	0.2576	6.54	33.61
3	0.2294	5.83	26.65
4	0.2043	5.19	21.14
5	0.1819	4.62	16.76
6	0.162	4.11	13.29
7	0.1443	3.67	10.55
8	0.1285	3.26	8.36
9	0.1144	2.91	6.63
10	0.1019	2.59	5.26

This application chart from an american manufacturer is a little bit more conservative:

Interesting is the use of alternator size instead of current demand.
The number of the current behind the cable diameter is the fuse size!

Alternator rating	Up to 15ft	15ft to 20ft	20ft to 25ft	25ft to 30ft
70 Amps	#8 ga. / 50 Amp	#8 ga. / 50 Amp	#6 ga. / 50 Amp	#6 ga. / 50 Amp
95 Amps	#8 ga. / 50 Amp	#6 ga. / 50 Amp	#4 ga. / 50 Amp	#4 ga. / 50 Amp
130 Amps	#6 ga. / 80 Amp	#4 ga. / 80 Amp	#2 ga. / 120 Amp	#1 ga. / 80 Amp
160 Amps	#4 ga. / 120 Amp	#2 ga. / 120 Amp	#2 ga. / 120 Amp	#0 ga. / 120 Amp
240 Amps	#000 ga. / 150 Amp	#000 ga. / 150 Amp	#0000 ga. / 150 Amp	#0000 ga. / 150 Amp

[Deezelweazel]

12. External Charging

Batteries love to remain charged at all times.
This is a problem. Sometimes driving time is to short to recharge the batteries properly.
So i had the idea to add an extermal battery charger which can be added to the mains if necessary.

Having good experiences with the brand C-Tek, I bought an additional C-Tek battery charger with a maximum current capacity of 10A.



I like this device for several reasons:
- high current output which is within the current specs. of the batteries
- external temperature sensor, adjusted charging to the environment
- choice of clamps or permanent battery eyelets
- fully automatic. Once charged, it switches into float charge.
- extra program for AGM batteries
- can function as a power supply





The only problem I see is that it is a pricey unit. You simply can't leave it outside unattended or it's gone.

So I had the idea of using an external mains power supply with a permanent mounted inlet into the bumper. nobody is going to steal an extension with a special plug...
The C- tek unit has already four mounting holes at the casing to mount it somewhere permanently.

The socket to be mounted in the bumper has a spring lid. Preventing the entry of dirt, mud and water.
On the left the extension cord on the right the amoured and shielded supply line with the bumper mounted inlet. This line must be properly grounded to vehicles earth.



When I come home from work I simply plug in the green wire into the mains and the charger starts automatically at the preset position AGM to charge the supply battery. There is no supervision required. If necessary the charger can also charge the startewr battery, both have a quick connector for the charger.
I can leave it in as long as I want, it does switch automatically into float charge.

The extension cord fits nicely in the Range bag.

[Deezelweazel]

13. Sources & Costs

What did I spent for this set-up?

necessary:
-Optima Yellow-top 200€
-Welding OFC Cable 35mm² 100€
- Battery Diode Isolator 100€
- Fuses, 4 EA 24€
- fuse holder, 2EA 40€
- ring terminals 16€
- heat shrinking tube 10€
- quick disconnects or battery terminals 20€

-----------------------------------
add-ons I wanted to have:

+ alternator overhaul: new brushes and bearings 50€
+ Ctek charger 10A 150€
+ mains connector 90€
+ Battery Monitor 120€
+ 5.11 tactical bag 80€
-----------------------------------
total 1000€
If you are shocked about the costs- I was too.
It took me quite a time to accumulate all the stuff and to think about it.
Just have in mind that a coolant engine heater costs an additional 1000€. You simply can't skip on power supply if you demand reliability.

Sources:
I have written a couple of questions to the manufacturers and I want to thank Sure Power industries for their quick and more than sufficient response. In fact, they provided me with a bunch of information!
They even added some nice stickers for free!!
Most highly welcome, thank you!

Optima batteries was the worst.
They didn't even feel the need to respond to E-mails.Not very cool- on their website they claim to stay in touch with their customers.
Well, lesson learned-In the future I will spend my money where I have the feeling to be welcome.

Electronic:
- Sure Power Industries
- IBS
- Hella
- Blue Sea systems
- Votronic
- NASA
- Mastervolt
- Sterling
- C-Tek

Batteries:
- Odyssey batteries
- Johnson controls (Optima and Varta)
- Exide
- Sonnenschein(now Exide)
- Lifeline

Only brand names are mentioned (cheap manufacturers do not provide any useful battery information on their products)

Names and brands being mentioned are not in an specific order.

I will neither post circuit wirings nor examples- the internet if full of them. just do your own research. I spent already more time in this as I wanted in the begining.



I have to mention that I'm neither responsible for failure or difficulties on your own projects since I can't check them. I took the greatest care to put the information together on this site - Being a human I can not guarantee completeness of information.

I do not recommend the use of any brand nor do I work for any of the mentioned companies.
Some of the brands being mentioned here work along with military specs.
As a reminder:
This means: Substantially modified commercial items! This also contains the environment in which it must operate without fail.