Maximum battery amps for 1GM

[mikecontessa26]

Hello, i'm looking to maximise my battery power and minimise my charging time, i'm planning on installing two 40W solar panels and would like to get up to 180amps of domestic battery power.

I understand my 1GM would just about cope with 120amps with it's current alternator, does anyone know if i can get an upgrade and how much it would cost?

Thanks,

Mike

 

[Tranona]

Merlin sell the Balmar uprated alternators and have a model for Yanmar with a maximum output of 70 amps - twice standard. I assume it will work with a 1GM but don't have any direct experience. Not cheap - around £300, but actually not much more (I think) than a new standard Yanmar unit. Details on their site www.power-store.com or give them a call on 01202 697979

 

[BobnLesley]

Is the 1GM the 10hp single cylinder motor?

I'm no expert but for comparison would report that we have a Volvo MD6A (10hp twin) from which we comfortably charge 2 x 90 amp/hr domestic and 1 x 55 amp/hr starting batteries. The 'standard' 35 amp alternator has been dumped in favour of a 65 amp one - recon job off a either VW Polo or Golf as I remember plus a Sterling Smart Charger/Alternator thingy. Whilst I'm sure the Balmar units are very pretty, 300 is a lot of beer tokens; having taken our U/S original to the local Auto Electrician he advised on a similarly sized (physically) unit with equivalent holes which he could supply s/hand & reconned and to which he fitted our original pulley; it cost £70 and re-fitting was a straight swap. If you want to sail and not motor for half the day, then get the Sterling Smart-Charger Unit, they're about £120 and make a huge difference.

 

[lw395]

I presume the original poster meant Amp-hours as units of 'battery power', or rather battery capacity. The original 35A alternator will charge these albeit slowly, particularly at low rpm. In the yanmar manual there is a graph of max current vs engine rpm, even a smart controller sterling thingy won't get more than this from your alternator, so if you want to improve on recharge time, then a more modern alternator will help, particularly when combined with a multistage controller. I fitted a bosch from a mondeo to my 3gm, big improvement as the bosch produces something like (up to) 110A at max revs and 80A at fast tickover.
If you're being picky, the charge rate is also a little less if there is a splitter diode pair in the way as the alternator works into a higher voltage.
A smart controller also gives the 'fan' belt an easier life by ramping up the charge on start up. This is well worthwhile in my experience!
So if you want an economical upgrade, £20 alternator from scrap yard, £120? sterling controller. Make sure the alternator goes in the engine box, they're fatter!
Hope that helps?

 

[wiggy]

I use sterling alternator regulator on my 1GM10 to charge 2x120amp house batteries. seems to work fine, if you it a larger alternator you need to consider how many HP it will take of your 9 available.

 

[lw395]

That's true, 1hp = 742 Watts ?
50% efficient?
So every 10 Amps of charge will take about 0.4HP. (ish)
Without a smart charger, I believe a really big alternator can make a small diesel refuse to start.
I think its more about getting 30A or so at fast idle than getting 100A at max revs.
The batteries will only take a certain current, which generally tails off to a steady level after a few minutes, so I tend to let the batteries charge for a few minutes before switching on the fridge if charging at idle. At higher revs, the torque to turn the alternator is reduced, because the power is regulated effectively.
You can see why modern cars have multi-vee alternator belts to handle the power!

 

[steve28]

is this a 1gm or a 1gm10, if its a 1gm then the sterling alternator controller will suck all the life out of the engine if the battery is remotly flat.
1gm10 = 9hp
1gm = 7.5hp

 

[andy_wilson]

The alternator will never prevent the engine from starting, but I can say from experience that it can prevent the engine producing any RPM when the prop is engaged with flat batteries.

RPM at start up are insufficient to excite the aternator, that is at a maximum at about 1500rpm typically. At which point, with very flat batteries a 100amp alternator will have first refusal on about 4hp... which is about all the engine will produce at those rpm. The result is the engine never reaches 1500rpm, but hangs at some lower rpm until the batteries have had their first gulp of current. The charge rate drops dramatically without a smart charger.

Fortunately at the same time the engine is warming up and producing more power as the demands of the alternator lessen. But put her in gear too soon and you will find with such a marginal set-up that there will only be between tick-over and 1500rpm available to drive the boat, until the alternator demand drops.

Smart controllers which boast 'ramp up', when I investigated more fully were a bit rubbish. One actually didn't charge at all for 10 minutes, then just kicked in... not much of a ramp. OK, long enough to get the engine warmed up and get you underway, but in some cases, only just enough to get you off your mooring or out of the marina and get the sails up - result, no charging!

I have a manual set up and am very concious if I ever need to 'clear out' in a hurry, and start up with the domestic battery coupled in, that I might get the anchor up and be unable to drive out with any force.

Just a thought!

 

[DaveS]

[ QUOTE ]

Smart controllers which boast 'ramp up', when I investigated more fully were a bit rubbish. One actually didn't charge at all for 10 minutes, then just kicked in... not much of a ramp. OK, long enough to get the engine warmed up and get you underway, but in some cases, only just enough to get you off your mooring or out of the marina and get the sails up - result, no charging!

I have a manual set up and am very concious if I ever need to 'clear out' in a hurry, and start up with the domestic battery coupled in, that I might get the anchor up and be unable to drive out with any force.

Just a thought!

[/ QUOTE ]

The point about doing adequate research is well made. There are quite a few smart alternator manufacturers - not just Sterling - and while they all do the same basic job, they have different bells and whistles. My Merlin unit certainly does ramp up - observation of the ammeter gives simple confirmation of this. Some others do this too, but some don't.

One of the arguments against a smart controller is that by taking more power from the alternator it can, with a small cold engine, leave too little for effective propulsion. A switch placed in the controller's power lead, however, means that quick reversion to conventional charging can easily be achieved if so embarrassed...