Charging a Gel Cell off a car alternator

[Splat]

OK it's not boat related but I figured I'd get the best response here. I need to run a deep cycle battery in parallel with my trucks main battery to run radio equipment and a small lightbar at public service events. I intend to separate them with a ACR.

Now the question. My truck puts out a measured voltage around 14.3-14.7v at cruising rpm. The battery I have is from a power scooter and fits under my rear seat perfectly. it's stats are http://www.mkbattery.com/images/MU1SLDG.pdf

They list a charging voltage of 13.8-14.6 This is fine
a float voltage of 13.4-13.6 this is where I question. I not familiar with Gelcells, do I need to worry about charging these directly in parallel with my regular battery? or do I need to find a way to regulate the voltage as the battery tops off.

Bill

 

[wire2]

Re: Charging a Gel Cell off a car alternator

Current is more of an issue rather than voltage, with a gel-cell. You could connect it directly to the alternator and feel it every 5 minutes during a charge. If it gets hot, there's too much current through it, (induced by the alternator output voltage). A simple way to reduce voltage (which will limit current) is connect a headlamp bulb in series with the + lead. It will take longer to charge.

If you really want to get fancy, can build a charge circuit with a 7815 voltage regulator chip and a 1N200 diode in series with the output, to the base of a 2N3055 pass transistor. That will give an output of 13.60v

 

[jhebert]

Re: Charging a Gel Cell off a car alternator

OK it's not boat related but I figured I'd get the best response here.

I disagree with your assumption.

 

[Splat]

Re: Charging a Gel Cell off a car alternator

Current is more of an issue rather than voltage, with a gel-cell. You could connect it directly to the alternator and feel it every 5 minutes during a charge. If it gets hot, there's too much current through it, (induced by the alternator output voltage). A simple way to reduce voltage (which will limit current) is connect a headlamp bulb in series with the + lead. It will take longer to charge.

If you really want to get fancy, can build a charge circuit with a 7815 voltage regulator chip and a 1N200 diode in series with the output, to the base of a 2N3055 pass transistor. That will give an output of 13.60v

Thanks, yea If I can't connect it in parallel with a simple ACR and no additional circuitry I won't do it that way. I would rather mount a larger capacity true deep cycle battery to a frame rail under the truck so it can freely vent and outgas without worry. this setup has to be reliable, and I was to stick to KISS as much as possible for this one. Thanks tho.

Bill

 

[Splat]

Re: Charging a Gel Cell off a car alternator

I disagree with your assumption.

Which part?

Bill

 

[fucawi]

Re: Charging a Gel Cell off a car alternator

All you need is a diode from radio shack rated say 10 A 50 v or more in your live connection wire ...this will stop the gel cell discharging into the main battery and drop the voltage by 0.7v ..current is not an issue as batteries are self adjusting for current KISS ..listen to Fucawi

 

[kahuna123]

Re: Charging a Gel Cell off a car alternator

I ran group 31 gels for 12 years in my boat with a "car" alternator. There really is no difference except for the screen. Never had an issue, Gels will not take too heavy a discharge or charge. Once the plates get hot the gel will pull away from the plates and there ruined. I always bought them used for 35 each and got at least two or three years out of them before either they went bad or I left something on. But keep in mind our season is 12 months long. And yes they had no trouble stating a perkins 6 cylinder.
I ran them mostly because the location of my batteries made them almost impossible to service.

 

[boat1010]

Re: Charging a Gel Cell off a car alternator

Just make sure that if someone sits on the seat that it is under it doesn't short it out. Ummm.. Don't ask how I know that...LOL