My first MEP-701A / couple questions

[MidKnightBomber]

I wonder how long it would run without a DC charging system?

 

[chadande]

Anybody know for sure?

I've only run mine for an hour or so at a time. I'd say you could connect a battery charger off the convenience outlets if you needed to run for a long time. Or slave the genny off a truck.
The draw of the stuff that runs off DC after starting would be pretty low I'd guess.

 

[MidKnightBomber]

I would agree. I guess I am thinking more along the lines of backup power to a home. If the power is off at your house then the only power available to run a charger on the Batteries would be from the convenience outlets on the front of the Generator. I don't see why this wouldn't work to back-charge the batteries if you have a bad DC voltage reg

 

[steelypip]

It works and several members have done it, as the MEP002A/003A gen sets also have flaky shunt regulators to charge their batteries.

My only caution would be to size the charger maximum current rating to the batteries - you don't want a 10 amp charger on motorcycle/riding mower batteries, as the high initial charge rate would cost you some power and some electrolyte but not get much of a rate of charge.

My plan (house outage backup system, as you're talking about) is to have a 14/2 outlet feed from the house main panel to near the generator and plug that into the charger/maintainer for the generator batteries. When power goes out (and stays off long enough - we tend to give it a couple of hours), you go start the gen set. If the internal charging circuit on the gen set is disabled, you turn the 'generator shed' breaker back on after setting the transfer switch to generator power, and that keeps the batteries charged exactly as they were on line power.

If, on the other hand, the gen set charging system works OK, you leave it off, which is easy in my case, as the SOP is to turn all the load breakers off before transferring to generator power, and then add them one by one as needed.

If you're talking about a remote, off-grid site with a generator for use when you're there, and waiting most of the time you put a big 'solargizer' charger/desulaftor panel on the roof of the generator shed and call it done.

The one gotcha is that you never want to backfeed the regulator-rectifier on the generator set with an external charger with a higher cutoff voltage. The gen set charging reg-rec is a shunt design like most motorcycles have, meaning that it tries to dump excess power to ground to pull the voltage down to the magic number. The power transistor is sized for the output of the generating coil on the set, not a big plug-in battery charger, or the charging system of a vehicle. This problem is probably why most of the bad ones are bad.

 

[MidKnightBomber]

That's a good point I admittedly didn't think of.
Since I would be trickle charging the batteries from my home power when I have to switch over to generator power the trickle charger would continue to charge from the gen's power.

Would a 2.5 amp charger be a good size to use? Too big or too small?
Like this?

http://batterytender.com/products/industrial-applications/power-tender-plus-24v-at-2-5a.html

 

[steelypip]

The 2.5 amp model is a good general-purpose one - big enough to top up a vehicle battery, but small enough that it's unlikely to hurt a motorcycle/mower battery. I see that one is weatherproof, which might be good for your application. Which battery are you using?

If you're planning on keeping the thing on a trickle maintainer I really like the 3/4 Amp wall-wart model. It'll take days to recharge a depleted battery, but it will do a fine job keeping just about anything under 30 amp hours topped up. Meant for motorcycles, so it comes with a long cord with a polarized disconnect plug and both crocodile clamp and ring lug connector ends as options. You put the wall wart on the socket, all of which are under weather protection, and just run the low voltage lead over to the gen set battery.

 

[Crawdaddy]

I have one of the chargers that MidKnightBomber linked to installed on my MEP-016b. The onboard charger is dead so I use it instead. It fits perfectly in the triangular section of the frame on the front right below the control panel. It seems to work fine for keeping the 2 lawnmower batteries charged and comes with the added bonus that I can keep it plugged in year-round to make sure the batteries are charged and when I have to fire up the genset, I just plug it into the convenience outlet.

 

[MidKnightBomber]

I also have two lawn mower batteries installed

 

[Chainbreaker]

Presently my generator's charging circuit works but if it should fail I'm already setup. I use 2 Battery Minder 1500's (12V 1.5 amp) on my MEP-002a to maintain them. As an added benefit I can unplug them anytime and use them on other 12V batteries that might need topping up (lawn mower etc.). The BM 1500's work very well and have an automatic desulfating phase and are temperature compensated. Keeps sitting batteries tuned up nicely. I also install a battery shutoff switch in place of the crossover battery connection which eliminates any power to panel etc. and keeps the two batteries electrically isolated from each other until time of use. Although it's really not necessary to have the battery cutoff switch when using two 12V chargers as each charger only sees what is between its own terminals.



Here's a link, the "Education" page is very informative. You can find the BM-1500 around $50 on Amazon.

http://batteryminders.com/