Emergency battery charging

[Brahmany]

Hi All,
One of my sailing buddies has a xantrex truecharge 40 which has suddenly gone dead. He was thinking of connecting his cheap car battery charger to his solar sun saver 20 input as an emergency until he gets the xantrex sorted out. We are thinking the the sunsaver should behave the same as receiving a solar input temporarily. Any comments are appreciated.

 

[woodster]

are the batteries low now if not why not do the sorting out now and start with checking the xantrex and make sure it getting power and check the fuses between it and the battery connections

 

[smokey73]

I understand the desire to use the car charger in a temporary mode until you get the boat charger sorted or replaced. What I don't understand why you want to run it through the solar regulator. Why not just put the charger on the battery directly. If you're worried about doing something to the 12 volt electronics on the boat then disconnect the battery while you are charging it? What is the purpose of feeding the solar regulator from the battery charger? I wouldn't want to do this for a long time but using the car charger directly on the battery for the short term probably wouldn't do too much harm to the batteries.

 

[Brahmany]

Unfortunately things don't always go wrong dockside. The boat is in a very remote location and will be so for a while. Everything runs on 12 volts but has access to 240v power as I said earlier. As the house batteries are very expensive and the boat full of electronics we thought the extra protections of the solar regulator with a proper and controlled charging cycle would be a benefit to everything and enable the continuous use of appliances without connection/disconnection and generally mucking around until there is access to a new charger or repairs. Cheers

 

[dparilla]

I would not hook up the charger to the solar regulator, it will not do any good nor will it provide any additional protection. For that matter, I would not under any circumstances, leave a car battery charger connected to an unattended marine battery system on board. Car battery chargers are typically dumb chargers and will not adequately float charge the battery. Additionally, they are not ignition protected and could cause an explosion in the presence of hydrogen gas in the closed compartment of a boat. Lastly, I have seen case fault grounding in cheap battery chargers that caused excessive electrolytic damage to the boat due to stray AC current finding its way into the DC side. If you don't think the solar panel is up to the task of maintaining the boat, I would rather invest in a small auxiliary battery that you could use to start the engine if the on board bank is too low. Reducing your onboard loads to a minimum and treating the boat as "stored" is your safest bet until you can install a proper on board charger.

Just my 2 cents.
Dan

 

[Benny17441]

Do not hookup any charger to your solar controller. The output of the charger is already regulated. You mention expensive batteries, go ahead and check the manufacturers recommended charging voltage as there are some types that cannot be adequately charged by a cheap car charger. If there is no problem with the charging voltage and your car charger has two or three stages you can connect it directly to the batteries. I would not trust one of those dumb single stage car chargers. If you intend on using alligator clips I would not leave the charger unattended but you may hard wire it by installing battery connectors to the output leads. You may likely not be able to use refrigeration and have to conserve power in other uses until you get your inboard charger repaired or replaced.

 

[JohnShannon]

Either way would likely work, but putting two chargers in series does run the risk of destroying one or two chargers.

The cheap auto charger will do fine bulk charging the battery. No such thing as smart amps.

Once the battery is approaching full charge then you start to see differences between smart and dumb chargers

So charge the battery but watch the voltage and current, and use your brain to apply the smarts externally by switching off the dumb charge when the battery is nearly full

 

[centerline]

there is NO GOOD REASON to hook the car charger to the solar controller... the risk vs gain does not pencil out.

the car charger is intended to be connected directly to the batteries, so there should be no problem with doing that, lest something abnormal should happen.

but the potential for expensive problems to develop within a second or two by hooking up the charger to the solar charge controller, is much greater without any real benefit....

when there is another option, it doesnt make sense to take a risk like that when you are admittedly in a remote area