Do battery isolators damage your deep cycle coach batterys?

JKFlipFlop wrote:
Ok, so I know the old style diode isolators have been around for ever and are still in use today.

Since they are diode based a .3-.6 volt loss is created and your batteries never get fully charged. Even a small voltage drop is significant because you shouldn't be discharging your battery below 60%-70%, and a battery at 10.5 is basically dead. So really your power range exist between 12-13V.

Another concern is that the new solid state isolators relay/solenoid isolators put in parallel your starter and aux bank when charging. If your deep cycle house battery is at 60%, and it gets bridged to your starter battery, you can get some serious current draw. over 100 amps. I don't know but I seriously doubt a deep cycle battery is meant to be dumped with 100+ amps, and not charged with a 3 stage profile.

In fact, I do not think an isolator exists that uses a 3 stage charge.

Thoughts?

You need to do a little more education gathering before condemning the relay based isolators and the charging of the deep cycle batteries, from the alternator, while driving.

First of all, you should have a good three stage charger for your normal battery charging needs. It is recommended by most all makers of deep cycle batteries that, if they are seriously depleted, you should recharge them using your multi stage charger, rather then expecting them to charge from the alternator while driving home, when ever possible.

With all that said, the higher voltage output, and high current producing capability, of the alternator is not the potential disaster you seem to think. Unless this is the only charging ever available to your batteries, and is done every day, all day, there isn't much danger of hurting anything.

The batteries will not be force fed the 100+ amps that you mentioned. A battery will only accept the amount of current that is needs to reach a full charge. The batteries control the current flow, NOT the alternator. While charging at the higher constant voltage is not optimum, it does little damage in the total scheme of events.

Again, the fact that the alternator CAN produce 100+ amps, when needed, it doesn't have any bearing on the batteries unless the voltage is excessively high.

These isolaters will introduce a voltage drop between the charger and the batteries and as a result, the batteries will never fully charge. I have been a marine service technician specializing in electrical and electronic systems for 40 years. While it will not become an issue immediately, it will significantly reduce the life of your battery. No type of battery charger will overcome this issue. We no longer use isolaters in the marine industry, instead we install battery combiners or chargers that allow the charging of separate banks. For RV's, an excellent option is a 3 stage smart charger to the coach batteries with an echo charger connected from the coach batteries to the engine battery. Your start battery actually needs very little charging capabilities when the coach is sitting, just enough to keep it topped off. Hope this helps. Chuck

I can't believe people still use those diode style isolators when MOSFET isolators are so much better. I use a POWER-GATE dual isolator on my coach and it's been reliable as hell.

Diode based isolators are not a big problem in RV's since they are NOT the prime charging source for the house batteries. They are quite capable of maintaining a good level of charge on those batteries from the alternator while driving. Unless the rig never sees shore power, to allow the converter/charger to fully charge the batteries, there will be no lasting ill effects.

The average motorhome spends many more hours on shore power than it does going down the road. The house batteries will see a full charge often enough.

Just a comment - we had an isolator in ours and the battery kept giving me trouble. I bypassed it, and now not one bit of trouble with battery or charging. I'm not a tech/mechanic, so have no clue why, but it worked well after we disabled the isolator on a road trip, so never hooked in back into system. have had no troubles in two+ years since.

monkey44 wrote:
Just a comment - we had an isolator in ours and the battery kept giving me trouble. I bypassed it, and now not one bit of trouble with battery or charging. I'm not a tech/mechanic, so have no clue why, but it worked well after we disabled the isolator on a road trip, so never hooked in back into system. have had no troubles in two+ years since.

Just because an isolator goes bad doesn't mean that it's a bad idea to have an isolator, or that the isolator was of a bad design.

If you ever have a situation that runs your house batteries down, unexpectedly, you will run your chassis battery down also, Battery isolators have their purpose even though you may never experience the need.

http://caravanchronicles.com/guides/how-to-connect-two-batteries-in-parallel/

I just found this article. What an eye opener. If you have 2 parallel house batteries, simply tapping the positive and negative terminals on the correct battery will make a big difference on lifespan.


update: ****, this site is a GREAT source.

$328 for an duel 150 amp isolator. Give me a break..
14.6 volt regulator is around $12 for a Delco 22si alternator. Don't have to worry about the isolator voltage drop.

A $12 voltage regulator doesn't resolve a volt drop between the alternator and the battery(s).....nor does a $120 voltage regulator, or a $1,200 voltage regulator. You'll always have a voltage drop to contend with as a function of physics. The question is "how does one minimize the voltage drop?" You can dial up the voltage to try to compensate, or try to minimize the voltage drop by selecting components and cabling that introduce as little resistance into the circuit as possible. You can try to dissipate the heat, or try not to generate heat in the first place. You can buy a well engineered RV with quality parts and pieces, or you can buy a dirt-cheap piece of sh*t RV and spend your life replacing crappy parts with more crappy parts....to each their own. I could have bought a $65 battery isolator from Harbor Freight, but I chose to spend more money on what I believed to be a much better battery isolator and so far, I'm pleased with my choice as I've had no problems and the multimeter indicates that the device does what it's supposed to do...eliminate the high voltage drop, not get hot, and keep my batteries isolated and healthy. IMHO dialing up the voltage regulator is asking for trouble as you still have a high voltage drop, and if/when the isolator fails/shorts, you may apply elevated voltage to your battery(s) and cause outgassing, overcharging, etc....so all of a sudden your $12 fix turns into the several hundred dollar battery adventure....no thanks.

sjholt wrote:
$328 for an duel 150 amp isolator. Give me a break..
14.6 volt regulator is around $12 for a Delco 22si alternator. Don't have to worry about the isolator voltage drop.