LT35HD 25hp Engine Stall

Rhodemont · November 22, 2021, 01:11:45 PM

Ran my LT35HD for couple hours. Was just finishing up and when I operated any hydraulics the motor would rev down the stall. Cleaned everything up and started up about 15 minutes later. All was ok for a couple minutes then started to rev down and stall again. Waited a few more minutes and would not start. Ah low/dead battery. So jumped a spare battery on an all ran fine. Pulled battery and put on charger...yep down to 20%. So why would hydraulics stall motor when running? Thought it should be generating enough 12volts to operate hydraulics(and keep battery charged). Do I need to check voltage output on motor or write it up to 5 year old battery?

Southside · November 22, 2021, 01:19:36 PM

With no reserve in the battery a full draw by the hydraulic pump at idle is just too much load so the engine dies. At WOT the engine can keep up with the load the alternator is pulling.

Not that it is likely making a difference but check the heat sink generator on the left side by the throttle spring. It is supposed to be disconnected when a belt driven alternator is installed. Mine was connected and eventually failed causing me electrical issues.

Rhodemont · November 22, 2021, 02:16:51 PM

That is what I was thinking. We our first cold nights and the battery had enough to start up and run but not taking and charge and finally was too low. It has charged up in the shop so will give it another chance at life and put it back in but realize same thing will likely happen.

I will look at that heat sink generator...would not even know it was there to look at.

Rhodemont · December 13, 2021, 11:09:02 AM

It was a broken alternator belt. You would think I would have seen that right away but it was tough to see with the cover guards in place.

Ben Cut-wright · December 13, 2021, 11:59:26 AM

It is amazing how many instances of charging issues involving the LT35 in particular, it seems.

@ southside: The component you refer to is a regulator/rectifier for the flywheel dynamo. Was the output connected to the rest of the electrical system before it was disconnected? Was this a replacement engine unit or did it come from the mill manufacturer that way? Please forgive another question? What issues occurred with the charging circuit connected to the external regulator/rectifier? There are several possibilities, only wanting to hear what you confronted.

Thank you for your patience.

YellowHammer · December 13, 2021, 12:19:56 PM

I would agree, the hydraulics operates off a starter type motor, very high amperage, much higher than the alternator can provide by itself. The battery serves as a reserve, and allows the high amp hydraulics to operate. With no battery or a dead battery, I could see how when activating the hydros there wouldn't be enough electrical power to operate the mill engine.

It may also be that there is a voltage cutoff on the engine, when the hydros are activated, the alternator can't keep up, the voltage drops below a threshold and the engine cuts off.

Southside · December 13, 2021, 01:03:39 PM

Factory engine, was connected to the rest of the system, but WM told me it was supposed to have been disconnected when the engine was installed. I don't remember what the issue was, but disconnecting the unit resolved it.

SawyerTed · December 13, 2021, 06:06:15 PM

Quote from: YellowHammer on December 13, 2021, 12:19:56 PM
I would agree, the hydraulics operates off a starter type motor, very high amperage, much higher than the alternator can provide by itself. The battery serves as a reserve, and allows the high amp hydraulics to operate. With no battery or a dead battery, I could see how when activating the hydros there wouldn't be enough electrical power to operate the mill engine.

It may also be that there is a voltage cutoff on the engine, when the hydros are activated, the alternator can't keep up, the voltage drops below a threshold and the engine cuts off.

Some have solved this issue by installing a battery in parallel with the OEM battery.
I am considering this. Apparently, some are installing the second battery and connecting at the hydraulic pump. This only allows the second battery to charge when the head is on the copper strip.
Installing in direct parallel with the original battery means devising a second battery box that travels with the head. The advantage is the alternator will charge both batteries. A dual battery switch would allow selecting one or both batteries or turning them both off. Just don't turn the switch when the engine is running. It will toast the diodes in the rectifier.

Ben Cut-wright · December 15, 2021, 11:51:11 AM

@SawyerTed

My comments are directed towards your post but are in general and not holding your feet to the fire.

Whatever "issue some have solved" with two parallel batteries is not specified. The alternator is the primary source for electrical power...UNTIL...load causes voltage to drop below alternator output. At that time the battery/batteries begin to supply energy. More batteries WILL provide more reserve energy, but not without a cost. An alternator loaded to max for an appreciable length of time will NOT last, that is NOT the job an alternator is designed to do.

"Sparks" has written on this site that a battery should be *expected to be replaced annually. My experience with the belt driven alternator, a quality battery, regular battery/electrical system maintenance, and never allowing the battery to become even partially discharged, can extend the life of that battery by several years. A frequently discharged cranking battery will NOT last. It is damaged every time the charge falls below a threshold. Multiple batteries might NOT be a resolution for every situation. An alternator having to recharge more depleted batteries will not last longer. Suffice to say, an alternator works best and lasts longest when it is used to recharge a good battery quickly and is sized to accommodate an *infrequent maximum load.

The loads on a WoodMizer HD sawmill do strain the charging system, there's no doubt. A cooling upgrade kit can extend the life of the alternator a bunch. Keeping the battery maintained will extend its life no matter where it is used. Precisely WHAT is creating each problem in any particular situation is primary in resolving the issue. NO matter what repairs or upgrading is done, if it doesn't address the cause of the issue, it may only mask or alleviate it, not be a permanent repair.

Southside · December 15, 2021, 11:58:42 AM

In the case of a Wood Mizer the second battery gives you hydraulic function regardless of where the head is. That alone solves just about everything.

SawyerTed · December 15, 2021, 03:16:13 PM

Ben I don't disagree. In general parallel batteries provide greater amp hours and provide the increased reserve needed to operate the hydraulics without the excessive draw on one battery when the alternator amperage can't keep up.

The parallel batteries shouldn't need annual replacement because the current draw is basically halved between the two. The alternator should last longer as well because it isn't operating at the edge of capacity

Maine Miller · December 15, 2021, 03:38:15 PM

To travel with the head and be run parallel to the other battery would require cables to run with the head as well, correct? That seems like it would be a lot of work adding a flex track for the cables to run in.