My Split Charge Thread

[fridayman]

If I am fitting a 400A VSR: would 60mm2/415A cable with 2X400A circuit breakers be best to connect to the two positive terminals on the batteries? Or is this overkill? Should I rather be looking at 50mm2/345A cable with 2X300A circuit breakers? Cost wise there isn't much in it, both will be expensive... My alternator will only be charging at 80A or 120A max, but at some point I will be fitting a winch and I might need to link the batteries in an emergency - how much current do winches draw? Or I might link the two batteries if the starter battery is low/dead - how much current does the starter draw on a Colorado?

 

[AndyCook]

No idea myself if that is overkill or not
nor the current draw's

I will have to check the rating of the mega-fuses I have used. They have not blown so far, even with some linked battery starting and winching with batterys linked

 

[Jon Wildsmith]

If I am fitting a 400A VSR: would 60mm2/415A cable with 2X400A circuit breakers be best to connect to the two positive terminals on the batteries? Or is this overkill? Should I rather be looking at 50mm2/345A cable with 2X300A circuit breakers? Cost wise there isn't much in it, both will be expensive... My alternator will only be charging at 80A or 120A max, but at some point I will be fitting a winch and I might need to link the batteries in an emergency - how much current do winches draw? Or I might link the two batteries if the starter battery is low/dead - how much current does the starter draw on a Colorado?

OTT, 50mm2 is plenty. I'm using 250 amp fuses for a bigger safety margin and have done start and winch assist with the aux battery a few times without blowing a fuse.

 

[fridayman]

It seems current draw can vary between winches depending on size (obviously) but also quality. Have a look at THIS article. I am not sure if "motor current" is different to current draw but the measured currents went up to 345A maximum on a 9500lbs winch, with the factory maximum current of 480A (perhaps if the test was repeated a few more times the equipment would have heated up and reached this level).
Looking around a bit more, a Champion 12k-lbs winch has a max current draw rating of 380A (seems low).
HERE is another article that suggests 400A+ currents under severe conditions. A 12LBS SUPERWINCH can draw up to 530A, while their 9500LBS MODEL is rated at up to 430A.

What I have noticed is that for any given load, the larger winches will draw less current.

Tough decision when experienced members are saying less will do

 

[Jon Wildsmith]

Both batteries will be sharing the winch load, the ratio depending on their respective state of charge at the time but a side effect of that is that the voltage stays a bit higher longer and the more volts there are the less current is drawn. The 250amp fuses I have positioned at each end of the wire the joins the two batteries together so they only see the power between the two not the combined power.

 

[fridayman]

Both batteries will be sharing the winch load, the ratio depending on their respective state of charge at the time but a side effect of that is that the voltage stays a bit higher longer and the more volts there are the less current is drawn. The 250amp fuses I have positioned at each end of the wire the joins the two batteries together so they only see the power between the two not the combined power.

Jon, is your winch 12V or 24V?

If I understand this correctly - with the winch attached to the starter battery with cable A, and the leisure battery connected to the starter battery with cable B... when linking the batteries to winch, the current in cable B will be higher than the current in cable A?

 

[Jon Wildsmith]

My winch is 12v, my aux battery is switched in parallel with the starter battery. I only have those 2 batteries.

Cable A carries all the current to the winch, that is the power being supplied by both batteries (and the alternator). On my truck cable A only has a rotary cut out switch close to the battery that is normally off, there is no fuse on my cable A.

Cable B carries only the current the aux battery is contributing, for the sake of simplicity lets call it half the power usually although the exact ratio will vary and could go up or down On my truck cable B has a 250 amp fuse at each end because IMO if I blow one of those I want to be sure I know the reason why before I would go for a higher rating, that's a lot of power even for the short time it takes for a fuse to blow.

Someone else may come along and say they pop 250amp fuses without trying but I have not managed it. I have had a starter battery flat enough not to turn the engine over 2 or 3 times and so the aux battery would have supplied most of the juice. I have winched to the point of almost stalling the winch on only one recovery but repeatedly and for about 5 minutes.

Don't forget your alternator will be chipping in as a power source as well

EDIT: I'm only saying OTT because you asked. At the end of the day being happy with how you've done a job is an important part of enjoying our trucks so don't be too swayed by my opinion which I'm quite free with

 

[fridayman]

... the current in cable B will be higher than the current in cable A?

Oops, got that the wrong way round

 

[fridayman]

I'm only saying OTT because you asked. At the end of the day being happy with how you've done a job is an important part of enjoying our trucks so don't be too swayed by my opinion which I'm quite free with

Thanks Jon. I wouldn't ask lots of questions if I didn't want to hear the answers/opinions. For me, figuring this all out and learning/understanding it is half the fun

 

[fridayman]

A while back I was looking into mains battery chargers for my dual battery setup (for when we stop at powered sites). Where I ran out of answers, was when I was trying to understand if all battery chargers can be used as psu's? And if not, what makes a psu/battery charger different from other battery chargers. I bought one of THESE on ebay today. I still don't understand how it works, but this charger is designed to also maintain charge on batteries that are in constant use. It is also designed for a marine environment, so the back of my truck should be like paradise for this little unit.
Once I have my solar charging setup, I might not actually need this though (but the price was too good to pass up for now).

 

[fridayman]

The first step in this project is to isolate the 2 batteries, and then fit my Odyssey as the starter battery. I am going to place the starter battery on the right, near the fuse box. This looks fairly simple:
1 - remove the cable connecting the 2 positive terminals on the battery
2 - remove the cable running from the left battery positive terminal to the starter motor
3 - run a new 60mm2 cable from the starter motor to the starter battery
4 - replace old battery with the Odyssey battery

For those that have done this - what am I missing (before I start...)?

 

[fridayman]

What battery terminals have others used for there dual battery systems? They all look like they will only take 1 cable, and I need to connect at least 2 to each positive terminal (40mm^2 and 50/60mm^2). The screw post type might work if I use ring terminals on the cables.

 

[Jon Wildsmith]

Goodwinch have some with a stud that I used and they seemed pretty good to me and cheap - these - but you'll have to scroll down the page a lot to see them.

 

[Chris]

I used these

http://www.autoelectricsupplies.co.uk/p ... ategory/26

or these

http://www.vehicle-wiring-products.eu/V ... /bt526.jpg

Chris

 

[Gary Stockton]

I used some like these suspect they're the same as Jons link

 

[fridayman]

Thanks

I'm a little surprised by how much all this will cost in the end with heavy cable, good batteries, vsr, monitor, and a load of other bits...

 

[Chris]

Do you really need 60mm2 cable?

Chris

 

[SpinDrift]

Thanks

I'm a little surprised by how much all this will cost in the end with heavy cable, good batteries, vsr, monitor, and a load of other bits...

Yes, so was I. I rewired my split charge system at the end of last year and although I reused some stuff from my previous set up it came to over £400 plus around another £80 for a new leisure battery.

 

[fridayman]

Do you really need 60mm2 cable?

Chris

Only for the starter. The rest will be 40.

 

[fridayman]

I spent a bit more time planning my setup last weekend and came across a very good site that explains HOW INVERTERS WORK. Had to re-read a few bits, but very interesting. Also talks about why not to earth a DC-AC inverter.