How to "daisy-chain" 12V car batteries?

[USAPatriot63]

Does anyone know how to hook up an car alternator (for recharging) to a "daisy-chain" of 12V car/marine trickle charge batteries and connect them to a AC power inverter for the purpose of operating power tools or lights?

I saw this on The Colony and would like to learn how to do it and improve my skill sets. Thanks in advance.

[cherokeenut]

The thing you need to remember is follow basic electricity. If you wire the batteries positive to negative, that is called "wiring in series". That way will result in the battery voltage going up by 12 volts for each battery, 12, 24, 36 etc. but will not result in higher amprage. Wiring the batteries positive to positive and negative to negative is "wiring in parallel" and results in the voltage staying at 12 volts but the amprage dramaticly increasing with each battery, this is what you want to do. You want to use good heavy copper mulit braid cable such as 0 or 00 as this will help amprage loss between batteries. It doesnt matter where the charging source is hooked up, but I'd start at the first battery, it will equally charge all. I'd put the inverter at the last battery, but again it doesn't matter. Harbour Freight has great deals on 4000 watt inverters and I've had good success with mine. As a note they also sell solar kits that come with 3 nice sized cells, and all the stuff to hook up to your system. I bought three kits and just used the cells, they also have a high amp solar device that will allow you to tie all cells together (parallel remember) and then the device hooks up to the batteries allowing them to be charged during the day but not backfeed to the cells (damaging them) at night. As a note most auutomotive magazines are now running HF ads and usually have %20 coupons that come in very handy there. I usually go in with a handfull of them and buy one item, go back get another, and repeat untill my large ticket items are bought. You can only use one coupon per visit, no one said you had to leave the parking lot!

[MrDanB]

I like how you think Cherokeenut!

[TheLight]

If you're talking about hooking up your car's alternator to a second battery, look into getting a battery isolator. It prevents your main battery from getting run down by accessories like an amateur radio. It's wired like this:

Code: Select all

inverter -> isolator -> regular car battery
                     |-> accessory battery

Hooray for ascii art!

[Reddog]

If you are doing this in a vehicle, it becomes even more important to use an isolator as you do not want to start your car with the deep cycle battery. (I work in the marine industry where multiple batteries are common.) You might also want to investigate AGM (aggregated glass mat) batteries for this kind of application. They are much more forgiving, hold a charge better over repeated discharges, and recharge faster. They are a bit more expensive, (some of the boat batteries run upward of $250, but their specs are amazing) but in cases like this, where they will be run down then recharged a lot, they are worth it. Optima is the most recognized brand, but O'Reilly Automotive Parts has a house brand that has good specs for under $100, PLUS a 7 year warranty. (Optima is one or two depending on the battery.) I have one on a mini solar generator and it has been giving great service, even when I abuse it accidentally.

[xXx]

Not mentioned so I'll throw it out. Others with more knowledge can hopefully elaborate.

You'll want the batteries to be similar. An older or weaker battery will draw from a stronger battery when they're connected together.

[Snakatack]

"It doesn't matter where the charging source is hooked up, but I'd start at the first battery, it will equally charge all. I'd put the inverter at the last battery, but again it doesn't matter."

Actually it does matter, more than you might think. It is important to wire your battery bank as to balance the charge and load across your bank or your batteries will charge/discharge unequally. It's not a big hassle or expense to wire your batteries correctly. Check out this link: http://www.smartgauge.co.uk/batt_con.html

[repsfo]

Does anyone know how to hook up an car alternator (for recharging) to a "daisy-chain" of 12V car/marine trickle charge batteries and connect them to a AC power inverter for the purpose of operating power tools or lights?

I saw this on The Colony and would like to learn how to do it and improve my skill sets. Thanks in advance.

Several things to remember:

There are basically two types of batteries, Deep Cycle and Starting (car) and they cannot be mixed together..

Deep cycle should be slow charged @ 10-12 amps over 10 hours

Car batteries can be fast charged @ 60+ amps over <1hr

Car batteries will supply high current for short periods of time

Deep Cycle will supply lower current over longer periods of time.

Connecting a car Alternator to 6-10 Deep Cycle batteries connected in parallel would work for charging.

Connecting a car Alternator to 1 Deep Cycle battery will damage it.

Connecting a car alternator to 6-10 car batteries connected in parallel will destroy the Alternator.

Also disconnecting an Alternator from it's load (battery) while running will also destroy the Alternator.

[martiern]

Would this work? Just searching and found this example, any thoughts or ideas are appreciated.

[roger o]

Definitely will NOT work. You are connecting 2 batteries in series with 2 in parallel, so essentially you have an output of 24 volts not 12 - the batteries in parallel don't add to the voltage, the ones in series do. Your car alternator produces about 14 volts in order to charge the battery to 12. Your circuit has an output of 24 volts.

To the OP, the only way to do what you want is to use large Shottky diodes in a circuit to isolate each battery. Batteries, even brand new charge and discharge at different rates, so the strongest will take from the weakest etc. This is not a complex circuit to build, but unless you are familiar with electronics, is better left alone. The easiest way to charge multiple batteries is charge them one at a time.

[repsfo]

Would this work? Just searching and found this example, any thoughts or ideas are appreciated.

This picture is the typical way 6V golf cart batteries are used.

[HighDesertHawk]

"It doesn't matter where the charging source is hooked up, but I'd start at the first battery, it will equally charge all. I'd put the inverter at the last battery, but again it doesn't matter."

Actually it does matter, more than you might think. It is important to wire your battery bank as to balance the charge and load across your bank or your batteries will charge/discharge unequally. It's not a big hassle or expense to wire your batteries correctly. Check out this link: http://www.smartgauge.co.uk/batt_con.html

Great link with very pertinent information to the question.