Starter battery

[Nancy]

Having started my discussions with you on the subject of power chair batteries, I then started exploring the battery charger situation. The one recommended by BM needs some expertise so is not for me as I understand almost nothing about batteries. However, I do have a question. I carry at least one power chair (often two) in my van and the van has also been converted to a campervan so it also has two leisure batteries (so I can charge a chair whilst I'm driving). Yet, when I accidentally flatten the motor battery, despite the fact that I might have access to, potentially, six fully charged batteries inside the van, I call the AA to get me started. What bliss it would be to be able to plug in something to a three pin socket which is connected to the leisure batteries and then plug in to the cigar lighter socket and draw enough power to be able to start up. I'm sure this should be possible but have no idea how to go about doing this. Do any of you clever people out there know what to do? The van is a Mercedes Sprinter with the battery under the passenger side floor. I wouldn't be capable of accessing the battery itself to clip anything on to the terminals.

[440roadrunner]

I realize that hardware is different in the US and Europe, but here in the US, the solution would be easy. Either a battery switch, OFTEN used in marine installations, or one or two handy devices known as "continuous duty solenoids." They are called that because this defines them different from something like a Ford starter solenoid, which will burn up the coil if powered up for very long at a time. These solenoids are available here at any parts store/ marine/ RV supply outfit.

They look like:

http://cdn.racerpartswholesale.com/imag ... 01-100.jpg

An example would be a "typical RV" with an engine starting battery, and one or two batteries for RV power. In that case, the two RV batteries would be wired in parallel, but the main hot lead would be run to one of the posts of the solenoid, the other post going to the starting battery.

You can ALSO use two or more of these solenoids to isolate more than one battery if needed.

Now you need to energize the solenoid. Normally, the solenoid would be energized by the ignition switch, so that any time the engine is running, they will charge. When the key is "off" the RV batteries are separate from the engine battery.

So you leave your headlights on, etc, and run down the "main." What do you do? You previously have wired in a push button which will pick up power from the RV batteries, and momentarily apply it to the ignition terminal of the solenoid. As long as that button is held, the solenoid will energize, and you can start the engine. Then the charging system will hold the solenoid in for "normal" operation.

OR you can use manual battery switches

These come in all sorts of configurations, this one is "off", 1, 2, or "both."

http://a248.e.akamai.net/origin-cdn.vol ... 1349075235

[Burgerman]

Are they at 12v? Are they all AGM (seems quite likely) then I would just connect all of them to the cars alternator to charge. And also the chair. No need for anything complex. Other than an isolator (auto) device on your starter battery. So it doesent get used below a safe voltage.

I charge my chair directly extremely fast, as I drive directly from my vans alternator.

See here:

http://www.wheelchairdriver.com/faster- ... arging.htm

And the charger I use, allows me to charge my van from my chair, or my chair from my van... And any battery from one to another at up to 20 amps...

See here:

http://www.wheelchairdriver.com/hyperio ... harger.htm

There are other ways too. But having one with some cables would mean you can ALWAYS start your van, charge your chair, or charge the leisure batteries or whatever you want...

[440roadrunner]

BG a continuous duty solenoid DOES ACT as an isolater, and in my mind is much safer

If you are referring to an isolator which is two diodes on a heat sink, I have seen several of these fail with quite bad effects. At least two of these failures were in small boats, and one caused a bilge explosion

What happens with a dual -- diode isolator is that typically the "main" diode fails, which leaves the alternator only hooked to the alternative battery. This causes the regulator to "think" that the battery is dead, as the main buss is dropping, and meanwhile, the alternate battery is furiously being charged over voltage. Also, if installed on a "one wire" charging system, the main diode forward drop causes the battery running voltage to be down by that amount.

The other advantage of a solenoid isolator is just as I said -- if you run the main down, you can easily just push a pre-installed button long enough to jumper the two systems, start the car, and get things going.

[Burgerman]

http://www.prioritystart.com/

This, (there are many manufacturers) on starter only OR all batteries as one big battery as you prefer. Leaves plenty power to fire up.

Ideal scenario, use deep cycle and starter batteries in car, chair, lesisure etc. Like Odyssey.

Then hook the lot together with sensible sized cable, so you have 1 single big bank, and use this http://www.prioritystart.com/ to make damned sure it will always start. Because this setup means more starting amps, more reserve power, more deep cycle power and full alternator charge (100 amps ?) when you turn the key than any split system.