I have read all of the pages trying to find any mention of a separator used between the two batteries. I was under the impression this is a fairly easy way to go and essentially the same thing as an isolator I am just curious if that is true. If not what are the differences and or strengths of each? I am not at all confident working with electrical stuff but I just bought an optima yellow top for the back of my truck as the second battery. I have a fantastic vent fan for my utility shell that I plan on installing as well as an inverter and some lights for the back. I am trying to find a place to help me install it all and just wanted to make sure I bought everything in advance as well as having some idea of telling them what I want. Basically I just want a full proof way to have a dual battery setup without ever being able to kill my main battery for starting the truck. Thanks Tyler
How to make a cheap isolated dual-battery setup for $50
- Thread starter evldave
- Start date
Hi,
So, I must ask, is it worth having the limitations of your system verses the the added cost of a really good, versatile isolator system? In my mind, it is not. I have a fully isolated system that works extremely well. Sometimes saving a little money is money not well spent.
Sparky
So, I must ask, is it worth having the limitations of your system verses the the added cost of a really good, versatile isolator system? In my mind, it is not. I have a fully isolated system that works extremely well. Sometimes saving a little money is money not well spent.
Sparky
4RunAmok
Explorer
There is nothing limiting about the designs shown in this thread. You get nothing more in the expensive kits except a lighter wallet.
Speaking of limitations, battery Isolators cause a reduction in voltage that doesn't pass through from the alternator to the batteries, so they never get fully charged, solenoids don't have this problem...
dwh
Tail-End Charlie
There are two common ways to "isolate" batteries. One with with a diode type isolator. The ones with the big heat sink that you can find at any auto parts store. These have an issue of dropping the voltage across the diodes, so your aux battery ends up a little short of a full charge.
Then there is a solenoid - such as described in this thread. Since the solenoid is just a big electromagnetically operated switch, all it does is tie the batteries together into one big battery when the engine is running so they both get charged up to the same voltage. The solenoid setup is often called a "split-charge relay", but it does isolate when the engine is off and many folks call them isolators.
Then there are fancy setups that attach a little computer to sense voltage and energize the solenoid. One waits until the voltage on the engine battery side rises a bit before it ties the batteries, another will tie them if it senses rising voltage on either side (in case you have a shore powered charger on the house battery side).
What is presented in this thread is what you need.
A normal alternator/voltage regulator setup is simple and stupid. It's also a crappy way to charge batteries. Not really very different from a 30 dollar bench top battery charger, other than it's capable of many more amps - if your battery will allow that many amps to flow (usually, it won't). If that's what you are using to charge your batteries, then there is no need to get fancy with the battery isolator.
(Personally I run a dumb solenoid in my truck, as described in this thread - but I'm just a lowly journeyman electrician who put in 24,000 hours in the trade before I moved on to another career (designing and building computer networks) - so what do I know?
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dwh
Tail-End Charlie
What limitations?
HI,
For example, jump starting with this system requires jumper cables. Mine requires a flip of a switch which is much more fail safe. Also, mine is solenoid based. It has three modes. For winching, the batteries are totally isolated so as to not run down the starting battery under the winch load. Then there is the normal mode where the batteries operate in parallel and are charged simultaneously. Or I can emergency start the vehicle from the backup battery. This is the jump start mode. This is all under switch and solenoid control. With my system it is good to have identical batteries. I have two Odysseys bought at the same time.
I also upgraded my alternator to 160A. It was the largest I could find that would run off a V belt drive system. I would like to have an even larger alternator but it's a no go unless I'm willing to modify all of my belt driven accessories to a serpentine system. I'm not willing to go that far. So far, the 160A's has proven adequate. BTW, this dual battery system is installed on a 1989 YJ Jeep.
Sparky
For example, jump starting with this system requires jumper cables. Mine requires a flip of a switch which is much more fail safe. Also, mine is solenoid based. It has three modes. For winching, the batteries are totally isolated so as to not run down the starting battery under the winch load. Then there is the normal mode where the batteries operate in parallel and are charged simultaneously. Or I can emergency start the vehicle from the backup battery. This is the jump start mode. This is all under switch and solenoid control. With my system it is good to have identical batteries. I have two Odysseys bought at the same time.
I also upgraded my alternator to 160A. It was the largest I could find that would run off a V belt drive system. I would like to have an even larger alternator but it's a no go unless I'm willing to modify all of my belt driven accessories to a serpentine system. I'm not willing to go that far. So far, the 160A's has proven adequate. BTW, this dual battery system is installed on a 1989 YJ Jeep.
Sparky
dwh
Tail-End Charlie
The difference between what you just described, and a plain ol' dumb solenoid setup...is a 5 dollar switch.
So, there are no limitations.
But, if you add a 5 dollar switch, you get some extra options.
Identical batteries are not required in that situation. You've only got them tied when charging or jump starting. You are isolating them when the engine is off, or when winching. In none of those situations are identical batteries required.
Batteries are required to be identical when wired in series, or wired into a full-time parallel bank.
teotwaki
Excelsior!
I finally got a chance to go through this thread. Thanks for posting it up along with the nice pictorial diagrams! I run a similar system and it works great. If the batteries are seeing different uses (Deep Cycle & starting) then monitor the health of the deep cycle if it sees more hours of current draw such as from a fridge. If your drive times are short be prepared to occaisionally apply a good AC powered charger at home to keep the deep cycle battery healthy.
DWh has good thoughts on this stuff too.
DWh has good thoughts on this stuff too.
jjstahl3
Explorer
Here is a picture of my battery box I am almost finished with the install - I followed this thread and got together the parts - one question is if I hook up a winch to the starting battery is there something I should do while winching to protect the second battery in some way -
dwh
Tail-End Charlie
Well, as pointed out by Karma's post, you can add a switch to manually disconnect the solenoid and isolate the batteries so that the winch is running only from the starting battery and alternator.
dwh
Tail-End Charlie
Actually, it would be too much if it actually pumped 70a into the batteries. Luckily - it won't.
Depending on the batteries' construction and their internal resistance, they might never allow more than 10a or 15a peak to flow through them at the voltage that your voltage regulator is set at.
Depending on the batteries' construction and their internal resistance, they might never allow more than 10a or 15a peak to flow through them at the voltage that your voltage regulator is set at.